Referring to FIG. 1, a network device 10 includes a media access control (MAC) device 12 and a physical layer (PHY) device 14. The PHY device 14 includes a physical coding sublayer (PCS) device 16 and a serializer/deserializer (SERDES) 18. On a transmit path, an output of the MAC device 12 is input to a transmit PCS 20 of the PCS device 16. The transmit PCS 20 may perform 8 bit/10 bit encoding for 1000 Base-X. An output of the transmit PCS 20 is input to a fiber serializer 24 of the SERDES 18. In this example, the transmit PCS 20 receives data at 1.0 GHz and outputs encoded data at 1.25 GHz. The SERDES 18 operates at 1.25 GHz. The fiber serializer 24 converts the parallel data to serial data. The serial output of the fiber serializer 24 is output at 28.
On a receive side, serialized data is received at 30 and is input to a fiber deserializer 32, which converts the serial data to parallel data. The parallel data is output to a receive PCS 34, which may perform 8 bit/10 bit decoding for 1000 Base-X. An output of the receive PCS 34 is coupled to the MAC device 12. In this example, the MAC device 12 supports 1000 Base-X.
There are situations when it is desirable to support communications at different data rates. For example, it may be desirable to operate at 100Base-X rates such as 100Base-FX in addition to operation at 1000Base-X. 100Base-FX, however, utilizes a SERDES that operates at a lower data rate than the SERDES 18 used for 1000Base-X. 100Base-FX also uses a different type of PCS encoding/decoding. To address the dual speeds, conventional PHY/MAC devices employ two sets of SERDES, which increases the cost of the MAC/PHY devices and the network device 10.